Finland has inaugurated an industrial-scale sand battery this week in the southern town of Pornainen, where it'll take over heating duties from an old woodchip power plant for the municipality. It's set to reduce carbon emissions from the local heating network by as much as 70%, and is the largest…
Insulation and the thermal properties of sand ie it is good at storing heat. Think of it like a rock, it can store tons of heat but it takes a long time to transfer heat.
THIS IS NOT A BATTERY.
While it’s not a battery it mentions that they are working at heat conversion to electricity.
Yes, but even that would not make this a battery. Energy storage =/= battery. A battery is a type of energy storage, this is another type.